Lane markers, such as painted lane boundary markers (white lines) and raised markers, formed on a road work to divide the road into plural parts as lanes. Thus, in order to improve the running safety of motor vehicles, it is important for the motor vehicles in running one lane of a road ahead thereof to accurately recognize the lane markers formed on the road.
In view of the circumstances, white-line recognition systems are installed in motor vehicles. Such a white-line recognition system installed in a motor vehicle picks up an image (one frame image) of a region including a road ahead of the motor vehicle every preset time, and extracts edges of white lines marked on the road for each frame image picked up by the camera. In addition, the white-line recognition system successively stores the extracted edges for each frame image to thereby create a history of the extracted edges of white lines, and recognizes white lines marked on the road using the history of the extracted edges. One of these white-line recognition systems is disclosed in Japanese Patent Application Publication No. 2005-157670.